Gas turbines are used in many fields for driving generators or driven machines. In this case, the energy content of a fuel is used for producing a rotational movement of a turbine rotor. For this, the fuel is combusted in a combustion chamber, wherein compressed air is fed from an air compressor. The operating medium, under high pressure and under high temperature, which is produced in the combustion chamber as a result of combusting the fuel is directed in this case through a turbine unit, which is connected downstream to the combustion chamber, where it expands, performing work.
For producing the rotational movement of the turbine rotor, in this case a number of rotor blades, which customarily are assembled into blade groups or blade rows, are arranged on this turbine rotor. In this case, for each turbine stage provision is customarily made for a turbine disk on which the rotor blades are fastened by means of their blade root. For flow guiding of the operating medium in the turbine unit, moreover, stator blades, which are connected to the turbine casing and assembled to form stator blade rows, are customarily arranged between adjacent rotor blade rows.
The combustion chamber of the gas turbine can be constructed as a so-called annular combustion chamber, in which a multiplicity of burners, which are arranged around the turbine rotor in the circumferential direction, lead into a common combustion chamber space which is enclosed by a high temperature-resistant surrounding wall. For this, the combustion chamber in its entirety is designed as an annular structure. In addition to a single combustion chamber, provision may also be made for a multiplicity of combustion chambers.
A first stator blade row of a turbine unit as a rule directly adjoins the combustion chamber and together with the directly following rotor blade row, as seen in the flow direction of the operating medium, forms a first turbine stage of the turbine unit to which further turbine stages are customarily connected downstream.
In the design of such gas turbines, in addition to the achievable output, a particularly high efficiency is customarily a design aim. An increase in the efficiency in this case can be achieved, for thermodynamic reasons, basically by increasing the exit temperature at which the operating medium flows out of the combustion chamber and flows into the turbine unit. In this case, temperatures of about 1200° C. to 1500° C. are aimed at and also achieved for such gas turbines.
With such high temperatures of the operating medium, however, the components and parts which are exposed to this are subjected to high thermal loads. In order to protect the turbine disk and the turbine rotor against penetration of hot operating medium, provision is customarily made on the turbine disks for sealing plates which are attached in a circularly encompassing manner on the turbine disk on the surfaces which in each case are normal to the turbine axis. In this case, provision is customarily made on each side of the turbine disk in each case for a sealing plate per turbine blade. These overlap in a shingle-like manner and customarily have a sealing wing which extends as far as the adjacent stator blade in each case in such a way that penetration of hot operating medium in the direction of the turbine rotor is avoided.
The sealing plates, however, fulfill further functions. On the one hand, they form the axial fixing of the turbine blades by means of corresponding fastening elements, and on the other hand, they seal not only the turbine disk against penetration of hot gas from outside but also avoid escape of cooling air which is guided inside the turbine disk and is customarily further directed for cooling of the turbine blades themselves.
The aforesaid design of the turbine disks with sealing plates which overlap in a segmented, shingle-like manner, however, is relatively complicated. A relatively large number of sealing plates are required, which leads to a comparatively high construction cost of the turbine disks and therefore of the entire gas turbine. Furthermore, a possible necessary repair in the region of the turbine disks can be comparatively costly as a result of this construction.
A turbine rotor which is referred to in the introduction is known from EP 1 703 078 A1, DE 199 25 774 A1, GB 643,914 and DE 100 31 116 A1 in each case. In addition, it is known from U.S. Pat. No. 4,470,757 to adjust the amount of cooling air which flows into the rotor blade by means of plates which are provided solely for this.